


Got Your Back

by fuzipenguin



Category: Transformers: Robots in Disguise (2015)
Genre: Bestiality, Biting, Blowjobs, Fluff and Angst, Friendship, Gen, M/M, Mildly Dubious Consent, Other, Schmoop, Seduction, handjobs
Language: English
Status: In-Progress
Published: 2015-11-13
Updated: 2017-06-28
Packaged: 2018-05-01 12:06:21
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 6,683
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5205290
Author URL: https://archiveofourown.org/users/fuzipenguin/pseuds/fuzipenguin
Summary: <blockquote class="userstuff">
              <p>The progression of a relationship between Grimlock and Sideswipe, two self-proclaimed misfits of Team Bee</p>
            </blockquote>





	1. Throat Bared

**Author's Note:**

> Chapter 1: Sideswipe is behaving oddly...

                He doesn’t recharge much. It’s not due to choice, it’s just how he was built. So Bee assigns him nightly patrol more often than the others, especially as they’ve all adopted Earth’s day as their own and tend to recharge after the sun goes down.

                After relinquishing watch over to Strongarm a little after 3am, Grimlock heads over to his normal recharge spot in aisle four. The section of shelving at the far end nudges directly up against the mountainside and hosts Denny’s collection of antique iceboxes. Grimlock likes it back there; it’s one of the few places in the scrapyard without any smiling-faced statues of humans or humanized Earth animals.  

                He shudders. Those things can be damn creepy in the dark. He knows they’re lifeless, but he still doesn’t like it when they seem to stare at him.

                FixIt’s personal recharge berth in the Alchemor is still functional but the others generally recharge in their vehicle form scattered throughout the scrapyard. It’s primitive to sleep on the ground instead of plugged into a berth and privacy is laughable, but it’s all they have and no one complains.

                Well. Much.                                                               

                Gimlock’s own alternative form is not very conducive to recharging in. His tail gets in the way if he tries to lie on his back, and it’s difficult to get up quickly if he’s lying on his side. He has to resort to a lot of noisy flopping around because his arms are too short to leverage his bulk up. All in all, it’s just not worth it. So when he recharges, it’s in his base form, either on his back with his head pillowed atop his crossed arms or curled up on his side.

                Tonight he’s still pretty restless so he settles on his back and stares up at the stars, connecting the dots to make little shapes in the sky. He’s admiring Optimus Prime’s profile off near the horizon when suddenly there’s a scuff of sound off to his right. He startles and half raises up on one elbow, fists clenching.

                “Sorry, big guy,” Sideswipe’s familiar voice whispers and his optics boot up to full power, pinpointing his location in the darkness. He’s half crouched several feet away, hands held out in a non-threatening gesture. “Didn’t mean to scare you.”

                “Didn’t scare me,” Grimlock returns defensively, ignoring his surging fuel pump. “You just move all quiet-like. We should put a bell on you. What’s up?”

                Sideswipe shrugs. “Thought you might like some company.”

                Grimlock considers his friend. Sideswipe was usually oblivious to the world at this time of night. He recharged deeply and wherever he felt like, never picking the same spot. Grimlock had nearly stepped on him more than once after coming in from nightly patrol.

                Blinking in confusion, Grimlock gestures to his side. “Yeah, sure. Was just finding shapes in the stars.”

                Sideswipe eagerly moves forward, the glow of his optics illuminating his flash of a grin. “Sweet. One of my favorites. Although I like cloud watching a bit better, to be honest. They’re always changing. Scoot over, will you? I’m not gonna fit.”

                Without any warning, Sideswipe lifts his leg over Grimlock’s waist and steps into the small space between his side and the mountain. As Sideswipe finds his balance and begins to pull his other leg over, Grimlock hurriedly slides across the ground, raising up a small cloud of dust. He had assumed Sideswipe would sit next to him, maybe propped up against one of the scrapyard’s shelves.

                Not smush himself between Grimlock and the rock. Hadn’t the other mech said his greatest fear was not being able to move?

                Grimlock stares at Sideswipe as the mech plops down on his back, squirming around until he’s comfortable. One hand hooks over his shoulder so he can prop his chin on the back of his wrist, looking up at the night sky. The other rests atop his Decepticon Hunter he had removed from his back and placed at his side. He looks the very picture of nonchalance, but Grimlock hadn’t managed to move far enough over that they don’t touch. Their shoulders are brushing, and Grimlock is more than a little alarmed to feel Sideswipe trembling.

                Grimlock presses a little closer to confirm the shivers, and Sideswipe looks up at him questioningly.

                “Are you… you’re _shaking,_ ” Grimlock observes hesitantly.

                Sideswipe lifts his head to glance down the length of his body and then shrugs. “It’s a little chilly tonight.”

                Grimlock opens his mouth to comment on the fact that it’s eighty five degrees and one of the warmest days they’ve experienced on Earth yet. Then his admittedly slow processor catches up and points out Sideswipe’s guarded expression and the tense set of his shoulders.

                And Grimlock gets it. This is one of those things he actually _doesn’t_ get, but should shut his mouth about anyway.

                “Yeah, I was just thinking that. Hey, I can see Prime right there,” Grimlock offers, and is relieved when Sideswipe relaxes again, turning his head to follow the line of Grimlock’s pointing finger.

                They spend at least another hour identifying funny shapes among the stars. Around 4:30, Sideswipe’s optics start dimming and his words begin to slur. He looks to be on the verge of recharge, but with a shake, he fights it off and launches into a story about him racing on Cybertron.

                Grimlock watches Sideswipe fight off recharge three more times, confused as to why his friend doesn’t just sleep. Then Grimlock remembers the shivers which have since abated and the way Sideswipe had laid down, shielding his throat.

                It all clicks, and Grimlock’s pretty damn proud of himself for fitting the pieces of the puzzle together. It’s only been two days since Vertebreak had removed Sideswipe’s head from his body; he’d been relatively calm during the entire debacle and hadn’t mentioned anything since, but Grimlock could see how such a thing could plague a bot’s memory purges.

                He nonchalantly stretches, oh so accidentally pressing closer to Sideswipe. “Think I need to call it a night, Sideswipe. ‘m getting sleepy.”

                “Oh,” Sideswipe replies after a pause. “Yeah, course. I’ll just…”

                Before he can raise himself more than a foot off the ground, he’s halted by Grimlock’s hand on his chest. Grimlock gives him a puppy dog stare, one which Sideswipe himself had taught Grimlock. “You’re leaving? You’ve been keeping me warm.”

                Sideswipe stares at him in astonishment. Then something like a relived expression passes over his face and he relaxes back down. “Aw, poor widdle Dinobot chilly? Alright, I’ll stay. But I’m not a cuddler,” he warns, giving in easily.

                “Dinobots don’t cuddle,” Grimlock replies, offended at the very idea.

                Sideswipe chuckles and then the two of them quiet down. Grimlock hadn’t been lying when he said he was tired. Recharge is creeping up on him, and he feels his optic shutters beginning to close as the minutes pass. Next to him, Sideswipe fidgets for a bit before turning over onto his side. He draws his Deception Hunter close to his chest and his shoulders gradually tense up again.

                Grimlock watches him out of the corner of his optic, not sure what to do. Sideswipe’s roll has moved him out of touching distance, but only just.

                Debating with himself takes another minute, and then finally Grimlock makes a decision. Either he’s about to get punched… or this’ll work.

                Grimlock rolls to his side as well and shifts about as if he’s trying to get comfortable. He grumbles under his breath, twitching every few seconds before he finally scoots backwards until his back presses against Sideswipe’s.

                Sideswipe stiffens, and Grimlock stares wide-eyed down the length of aisle four, waiting for a smack to the back of his helm. Sideswipe’s probably pretty squished up against the rock face; in his nervousness, Grimlock had slid across the ground a little harder than he had originally intended to.

                The expected punch never comes. Instead, Sideswipe relaxes, going practically strutless against Grimlock’s frame. Grimlock gradually relaxes too, actually enjoying the feeling of another body warming his back. It’s kinda… nice. He trusts all the ‘bots, but Sideswipe had stood up for him when none of the others had, and for that alone Grimlock will always have Sideswipe’s back.

                He just never thought it would be this literal.

                Several minutes later, he’s nearly three quarters of the way into recharge when he feels a light touch on his hip. At first he thinks he’s imagining it. Then the touch turns into an affectionate pat.

                “Thanks, buddy,” Sideswipe whispers.

                Grimlock doesn’t reply. He doesn’t think he was meant to hear. So he just smiles to himself and slips the rest of the way into sleep.

 ~End


	2. Reassured

**Summary for the Chapter:**

> It's Grimlock's turn to need some support

                It’s not hard to find Grimlock. For one, he’s kinda brightly colored. And huge. There’s just not that many places within the junkyard for him to lurk in. Especially since certain sections have been placed off limits to all of them by Denny.

                Sideswipe finds Grimlock sitting on his aft at the back end of aisle four, his normal sleep spot. The others all have one particular area they gravitate to, especially if they want privacy for a short while. Sideswipe still hasn’t picked a spot yet. He’s never been one to settle for too long.

                “Hey, buddy!” Sideswipe announces cheerfully as he approaches.

                Grimlock doesn’t even look up. Instead, he hunches in on himself even further, doing his best to bury his face in his arms. They’re crossed, lying on top of his drawn up knees, giving him the appearance of a very miserable, and very large, sparkling.

                Sideswipe plops down next to Grimlock, leaning his back up against the natural incline of the mountain. He rests the back of his helm against the stone and crosses his arms over his stomach. His legs stretch out in front of him and he’s otherwise silent as he stares up at the pretty blue sky. It’s a lovely shade today, reminding him of a pair of optics he hasn’t seen in far too long.

                The silence stretches on, probably for longer than anyone thinks he’s capable of. But he _can_ be quiet and still when the need arises.

                By the time twenty minutes pass, Grimlock has uncurled himself a little. Every now and then, he peeks over at Sideswipe, little glances that Sideswipe pretends not to see out of the corner of his optic. It’s Grimlock who breaks the silence first.

                “Are they… mad at me?” Grimlock asks hesitantly, almost as if can’t decide if he really wants to know.

                Sideswipe languidly stretches his arms up over his head and then resettles after both shoulders pop. He turns his head to look over at his friend. “Who?”

                Grimlock huffs. “You know who! Bee and Strongarm and Fixit and Denny and Russell!”

                “Why would Russell be mad at you?” Sideswipe returns, frowning a little. He pushes himself up on his elbows and angles his upper body towards Grimlock.

                The Dinobot blinks a little. “I don’t know. Is he?”

                “No,” Sideswipe says with a little shake of his head. “Denny’s not happy about the damage, but you know he’ll get over it. He’s pretty used to it by now.”

                “He should be with a great big oaf like me around,” Grimlock mutters, ducking his head back down.

                “Aw, Grim. You’re big and you’re great, but you’re not an oaf, bro,” Sideswipe cajoles, bumping his shoulder against Grimlock’s side. “Yeah, it was kinda annoying to catch those ‘cons again, but we got ‘em, and the canisters are back to rights. No harm done.”

                “But there could have been!” Grimlock protested, his words a little muffled. “Denny or Russel could have been hurt!”

                “Yeah,” Sideswipe admits. “But they weren’t and now you know not to juggle the stasis pods. Right?”

                Grimlock fidgets slightly before he shifts enough to allow one optic to peer over at Sideswipe. “Yeah,” he mumbles. “But Bee…”

                “Oh, what about him?” Sideswipe scoffs, resuming his original position and looking up into the sky again. “He’s not perfect either and he knows it.”

                Bumblebee was a good guy, but he really needed to loosen up a little. It wasn’t like they were a military or even a police unit. Grimlock and Sideswipe followed Bee because they chose to, and it would do him well to remember that.

                Wasn’t like they had many other options, but still.

                “He was so angry,” Grimlock whispers. “He _yelled_.”

                “Grim – you can’t tell me you’ve never been yelled at before,” Sideswipe points out, raising an orbital ridge as he glances at the Dinobot.

                “Not by anyone who ever mattered,” Grimlock replies, hiding his face again.

                Sideswipe bites his lower lip in thought as he gazes at his friend. “Do I matter?” he finally asks.

                Grimlock’s head shoots up, his optics wide and earnest. “Of course! You’re my best friend, Sides!”

                “Back at ya,” Sideswipe immediately says, bumping shoulders again. “So then you should listen to what I’m saying. You messed up, but it worked out in the end. No one’s gonna kick you out or lock you up. It’ll be fine.”

                “…really?”

                Sideswipe rolls his optics. “Really. Promise. And even if it’s not, you know I’ll stick with you.”

                Grimlock bursts out of his huddle in a whirl of green and black limbs and flings himself atop Sideswipe’s chest. Unsurprisingly, there’s not enough of his chest to fit a large Dinobot and some of him spills over into Sideswipe’s lap. 

                “You’re the best, Sides,” Grimlock murmurs against Sideswipe’s shoulder.

                Sideswipe blinks up at the sky and then pats Grimlock on the back. Grimlock is _heavy_ , but the bulk of him is a good weight. This close, Sideswipe can feel the steady, slow thump of Grimlock’s spark and it causes a flare of homesickness to well up in him.

                He rationalizes that the tight hug he gives Grimlock is because the guy needs a pick-me-up, not because Sideswipe suddenly and terribly misses home.

                After a long moment, he starts shoving at Grimlock’s shoulders. “All right, Grim. I told you before, I don’t cuddle.”

                Grimlock jerks back, optics darting off to the side in a sheepish manner. “Right. Sorry.”

                “s’ok. You wanna head back now? I think Russell was saying something about another horror movie marathon,” Sideswipe offers, already missing the warmth of the other mech’s frame.

                “Do ya think I should? What if they’re still mad?” Grimlock asks hesitantly.

                “Pfft! I’m sure they’re over it,” Sideswipe replies confidentially. It really hadn’t been that bad of an accident. And they should all be used to mishaps occurring around Grimlock by now.

                “Do you think maybe we could get Russell to watch something else?” Grimlock asks, pushing himself to his feet. He reaches down and grasps Sideswipe’s upstretched arm, lifting him to his feet with ease.

                “Thanks, brother. Maybe. Why? Big bad Dinobot like you frightened by human ghosts?” Sideswipe teases. They begin making their way down the aisle towards the main passageway through the junkyard. “I thought it was just kitties you were scared of.”

                Grimlock sniffs haughtily. “I’m not _scared_ of them. They’re just…creepy,” he says and shudders. Then…” Hey, Sideswipe…”

                “Yeah, big guy?”

                “That’s the second time you called me brother,” Grimlock points out.

                Sideswipe freezes. “Did I?”

                He mentally backtracks his conversation and realizes that Grimlock is right. He glances up at the Dinobot, cringing a little. “I don’t…”

                “I like it,” Grimlock announces, looking away almost shyly. “Dinobots see each other as siblings since they’re so few of us, but there are some I’ve never even met. And the ones I have, I never really felt close to. Not like a brother. Not like I do with you.”

                Sideswipe smiles weakly. He wonders if he should tell Grimlock about… nah. It’s too complicated. And Grimlock is right; they _have_ gotten close. He trusts Grim to have his back which isn’t something he can claim of a lot of mecha.

                “Well, then I hope you don’t mind if it slips out every now and then,” Sideswipe says, starting to walk again. “Me – a Dinotbot for a brother. I wonder what they would say about that back home!”

                “No one would ever mess with you,” Grimlock says cheerfully as he keeps pace with Sideswipe.

                “You got that right, Grim,” Sideswipe says fondly, patting Grimlock’s arm. “But hey… just be careful. I trust the others, but I don’t want any ‘cons overhearing us calling each other ‘brother’; they might think they can use it as an advantage over us.”

                Grimlock pauses and cocks his head to the side in thought. Sideswipe has a moment’s worry that the other mech might take it the wrong way. Then Grimlock nods in understanding.

                “Yeah. Yeah! Dirty ‘cons would use any kinda trick, wouldn’t they?”

                “Without a doubt,” Sideswipe replies, feeling both a sort of relief and disappointment. Never one to examine his deeper feelings too closely, he and Grimlock keep chatting as they make their way back to the Alchemor.

                As soon as they see each other, Bumblebee apologizes to Grimlock for yelling so loudly; the rest act like nothing had ever happened. Within minutes, Grimlock is joking and laughing with everyone, no longer sporting the kicked puppy look. Russell easily agrees to watch the Star Wars trilogy instead of the horror films. And for someone who glitches out over kittens, Grimlock inexplicably finds Ewoks adorable.

                Which _Sideswipe_ can’t help but find adorable. Grimlock is a really great guy, all spark and strength. Sideswipe is proud to call him brother, even if he feels a little wiggle of unease as he does it.

 

~ End Chapter


	3. Seduced

**Summary for the Chapter:**

> Sideswipe has an odd way of confirming Grimlock's injury is healed, but he goes with it. 
> 
> *This chapter is the reason the entire fic went up to NC17/explicit rating. Also see the updated tags list. For further notes pertaining to the dub-con and bestiality tag see the end of the fic*

     “How’d it go?”

     Sideswipe straightens from his slouch against the Alchemor’s entrance and turns towards Grimlock, expression both expectant and concerned.  

     “Fixit says I’m 100%!” Grimlock announces, patting his side.

     Gently. There is a lingering ache there still that Fixit has reassured him will fade away soon.

     Sideswipe’s sharp optics catch the cautious motion. “Fixit isn’t a medic,” Sideswipe says with a frown. “Come with me.”

     He reaches out and grabs Grimlock’s nearest arm, tugging on it until he changes direction to follow Sideswipe. “Where are we going, Sides?”

     Sideswipe doesn’t answer. He just keeps walking, leading Grimlock down the familiar path of aisle four. Once they get to the edge of the rock Grimlock normally sleeps against, Sideswipe whirls around and steps in close. Grimlock just stares curiously down at the top of Sideswipe’s helm as the shorter mech starts patting Grimlock’s chest.

     “Whatcha doing?” Grimlock asks after a moment.  

     Sideswipe growls in frustration and takes a step back, gesturing at Grimlock’s body. “Transform would ya? I have no idea what’s supposed to be where when you’re like that.”

     It’s an easy enough request to honor; Grimlock was about to recharge anyway. But he still transforms carefully, afraid that that familiar sharp pain will bloom once more from deep inside as his internals rearrange themselves.

     It doesn’t, and he heaves a sigh of relief even as Sideswipe crowds in close again. With optics abnormally bright and hands oddly gentle, he explores Grimlock’s chest, sides, hips, and back. It tickles a little in some spots, but Grimlock chokes back the giggles. Sideswipe looks serious.

     Sideswipe’s never serious.

     “Sides… really… what are you doing?”

     “I’m making sure you’re not hurt,” Sideswipe replies curtly, gaze still fixed on Grimlock’s plating.

     “Fixit said…”

     “He’s not a damn medic!” Sideswipe exclaims, startling Grimlock enough that he subconsciously takes a step back, shoulders hunching inwards. Sideswipe gets loud sometimes, but not like this. He goes quietly sarcastic more often than not and he’s never yelled in anger at Grimlock before.

     “I’m sorry… Grim, I’m sorry,” Sideswipe immediately says in apology, holding his hands out to the side in a non-threatening mater. “I just… you got hurt and… you’re so tough I didn’t even know you could _get_ hurt. I… I was worried. ”

     He ducks his head as his voice turns so low Grimlock has to strain to hear him.

     “Oh.”

     Oh! That was why Sideswipe had been sticking close to him these past few days. Sideswipe had even taken to recharging at the beginning of the aisle, as if guarding Grimlock’s sleep.

     “Well, you don’t gotta worry. I _am_ pretty tough,” Grimlock brags, feeling warmth spread through him at Sideswipe’s concern over him. “Scrap, if it had been one of the others they’d probably still be laid up.”

     Sideswipe nods rapidly, arms wrapped around himself as he fidgets in place. He looks so small like that. Grimlock gives into the urge to reach out and pat Sideswipe’s shoulder.

     “I’m ok, Sides,” Grimlock says softly. “You’ve checked me over.”

     The shorter mech suddenly goes still. When he looks up, there’s an odd twist to his lips, one that Grimlock isn’t familiar with. Just as he is about to ask, Sideswipe’s arms drop to his sides.

     “Yeah. A little. But not everywhere. Do you mind if I check again?” Sideswipe asks urgently.

     It seems a little much, but where’s the harm? Grimlock would probably be the same if their positions had been reversed, obsessively checking Sideswipe over and over again to make sure there were no lingering wounds.

     “No. Go ahead,” Grimlock instructs, Sideswipe’s hands immediately returning. He touches everywhere, from the top of Grimlock’s head to the bottom of his feet. And this time, Grimlock isn’t holding back giggles. Rather, he starts to squirm for a completely different reason as some of the touches verge on caresses rather than clinical exploration.

     His lines embarrassingly warm, Grimlock silently thanks the Primes when Sideswipe finally takes a step back. Grimlock imagines Sideswipe should be satisfied but the other mech is still frowning.

     “You seem ok…” Sideswipe admits. Then almost as an afterthought, “…hey, open your panel for me.”

     Grimlock jerks as two of Sideswipe’s fingertips brush over the apex of Grimlock’s thighs. “Uh, Sides. I _definitely_ wasn’t injured there. Trust me, I think I would know that.”

     “Please,” Sideswipe begs, face turned up and optics looking into his beseechingly. “I just want to make sure.”

     There is no reason for Sideswipe to check over Grimlock’s interfacing equipment. His injury was much higher up. And even Fixit hadn’t checked there when he had done his exams.

     But Sideswipe seems so worried…

     The sound of his interface cover sliding aside is surprisingly very quiet, almost lost in the shaky ex-vent that Sideswipe produces. He leans over, peering at Grimlock’s interface equipment. Which begins to stir, of course.

     Mortified, Grimlock twists to the side and tries to cover himself. Sideswipe makes an irritated noise and bats Grimlock’s hand away.

     “Don’t. Let me see,” Sideswipe instructs and moves even closer.

     “Sides…” Grimlock whines desperately.

     “What, are you shy? Trust me, big boy… you’ve got nothing to be shy about,” Sideswipe comments, fingers ghosting over the head of Grimlock’s spike.

     Grimlock makes a choked sound in reply and then nearly bites his own glossa in half as Sideswipe’s digits stroke down to the moistened entrance of Grimlock’s valve.

     “Oh,” Sideswipe says, voice mild. “Have I gotten you a little worked up? Sorry about that. Don’t worry, I’m not a tease.”

     Sideswipe drops to his knees and all Grimlock can do is stare down at the other mech, utterly befuddled. Sideswipe looks up at him, the tip of his glossa peeping out as it swipes over his lower lip. His hands reach up and clasp Grimlock’s thighs.

     “Tell me to stop and I will,” Sideswipe announces. He waits a beat for Grimlock to respond.

     “’I don’t even know what you’re doing,’” is what Grimlock wants to say. But instead, he trails off after ‘I’ when Sideswipe ducks and takes the head of Grimlock’s spike in his mouth.

     Oh. That’s what he’s doing, Grimlock thinks to himself.

     Is this part of Sideswipe’s exam? Or had he noticed Grimlock’s arousal and decided to address it head on?

     Heh.

     Head.

     “Sides… Sides…” Grimlock whispers, hand hovering above Sideswipe’s helm.

     Sideswipe rolls his optics upward, mouth opening wide as he advances down Grimlock’s spike. The smaller mech’s optics are slitted, only the tiniest line of blue visible between the shutters. His expression is peaceful, serene, as if he is completely happy servicing Grimlock.

     Without even pausing his ministrations, one of his hands rises, sweeping through the air and capturing Grimlock’s wrist. He tugs until Grimlock’s hand lands on the back of Sideswipe’s helm. As soon as it does, Sideswipe’s optics shut completely and he hums deep in the back of his throat.

     The vibrations travel up Grimlock’s back strut, and he hardens completely so fast it’s painful.

     “Oh… oh, _scrap_ ,” Grimlock says. Then Sideswipe sucks and Grimlock’s head flies backwards, his fingers curling in against Sideswipe’s helm. That just makes Sideswipe move faster, more eagerly.

     “I… we…” Grimlock apparently loses the power of speech under the skillful lash of Sideswipe’s glossa.

     There is something… something Grimlock should say… but he just can’t seem to find enough processing power to string the words together. Then Sideswipe’s free hand ghosts lower, fingers brushing over the rim of Grimlock’s valve and flirting just inside.

     Grimlock’s knees buckle and he wobbles in place, pleasure streaking through him. He isn’t exactly untouched but he’s never been with someone as knowledgeable as Sideswipe who seems to know exactly how to suck and lick and touch in ways that absolutely wreck Grimlock.

     Sideswipe abruptly pulls away, and Grimlock unashamedly whines in disappointment. The other mech shushes him and pushes to his feet, one hand stroking Grimlock’s spike and the other pressing against his green chest.

     “Back up,” Sideswipe instructs, voice a little rough. His optics are bright, brighter than even when he’s fighting, and his lips are shiny with oral lubricant. Grimlock can’t look away, especially when Sideswipe licks his lower lip.

     Grimlock backs up, going where Sideswipe directs him. In just a few steps, the back of his knees hit something solid. The mountainside, Grimlock realizes.

     “Sit.”

     Sideswipe pushes on Grimlock’s shoulder and he lets himself fall backwards, aft fitting perfectly on a level shelf of rock. Those shiny lips of Sideswipe’s lift up at the corners in satisfaction as he steps between Grimlock’s thighs. Sideswipe’s head is now nearly at the same height as his.

     “You ok, Grim?” Sideswipe asks, hand falling off Grimlock’s shoulder. His other one continues to stroke and pull at Grimlock’s spike, continually strengthening the charge gathering at the base of his backstrut.

     “Yeah,” Grimlock croaks, optics locked on Sideswipe’s face. Then he blinks and drops his gaze when he hears a quiet click.

     Sideswipe’s spike is pretty, Grimlock thinks dazedly. It’s red with a black spiral, the thinnest hint of yellow on either side of the black stripe. It’s a nice spike, long and wide enough to fit well within Grimlock’s hand. Or mouth. He swallows the sudden excess of oral lubricant that wells up in the back of his mouth and reaches out to grasp Sideswipe’s spike.

     Ex-venting shakily, Sideswipe widens his thighs and slips his hand down past Grimlock’s, two fingers sinking into his valve up to the knuckle. Amazingly, Sideswipe keeps tugging on Grimlock’s spike in a show of coordination Grimlock would never be able to replicate.

     Grimlock hears a soft, wet noise as Sideswipe begins pumping his fingers in and out of his valve, Grimlock avidly watching. Sideswipe’s valve is as shiny as his lips, and Grimlock thinks about gently pushing Sideswipe onto his back and getting in close, watching Sideswipe’s digits move. He wouldn’t be able to watch long, of course. He’d have to smell and taste everything, glossa slipping into that pretty valve and up that gorgeous spike.

     Sideswipe’s hand shifts deeper and he moans, optics slipping shut. He leans forward, resting his forehelm on Grimlock’s shoulder and blocking Grimlock’s view. But he can still hear and he listens with hungry focus to the moist sounds. He doesn’t know how Sideswipe does it, stimulating both himself and Grimlock. Grimlock can’t manage anything other than the occasional squeeze of his fingers around Sideswipe’s spike. It’s too hard to concentrate with the hot, lean length of Sideswipe propped against him, ventilating hard enough to make Grimlock’s shoulder damp.

     He turns his head slightly, nuzzling the side of Sideswipe’s helm. He nibbles at whatever piece of metal he can find, jaw aching with the need to really bury his denta someplace more substantial. Sideswipe abruptly jerks back, optics wide and pale blue.

     “You ready?” he whispers, gently pushing Grimlock’s hand away from his spike. He shifts, straddling Grimlock’s lap.

     “Ready… ready for what?” Grimlock asks dumbly and Sideswipe smiles again, affectionately knocking his forehelm against Grimlock’s. Then Sideswipe’s hand holds Grimlock’s spike steady so he can shuffle forward and drop down on top of it.

     Grimlock’s hands shoot out to grip Sideswipe by the waist, the plating there creaking under his digittips.

     “Sides…” Grimlock chokes out. “What…?”

     “Thought it’d be obvious, bro,” Sideswipe returns, the lines of his face tense. Grimlock realizes that Sideswipe hadn’t taken him in completely. He is slowly sinking down, pausing every few seconds to accustom himself to Grimlock’s width.

     The words spark something in Grimlock’s processor. “Thought… I thought… aren’t we brothers?” he bursts out.

     Sideswipe lets out a shaky laugh. “Yeah… well… I’ll have to tell you about that sometime.”

     “Tell me what?” Grimlock asks, bewildered. He’s quickly losing all rational thought, although it wasn’t like he had a whole lot to begin with. Sideswipe’s valve is hot and snug, rippling every time Sideswipe moves.

     “They might see!” Grimlock protests next, but his hands reach around and stroke over Sideswipe’s aft instead of lifting him off.

     Primus. Sideswipe is so _pretty_. Grimlock had always thought that, from the moment he’d first laid optics on the mech. In those first few days, he had thought about something like this. But only distantly, wistfully. Sideswipe had never shown interest towards Grimlock or any of the others, in fact. When they had become friends, Grimlock had been happy because at least he could have that.

     Yet here they were, Sideswipe finally settling completely in Grimlock’s lap, Grimlock’s spike buried deep inside the other mech.

     “Don’t worry, I commed Bee earlier. I think I nearly gave him a spark attack when I told him what we were doing, but he’ll make sure the others stay away,” Sideswipe explains, wriggling experimentally in ways that make Grimlock see stars.

     “He knows? He knows we…”

     “I didn’t give him details,” Sideswipe says with a roguish grin. “Unless you’re into that sorta thing.”

     In answer, Grimlock growls and tightens his grip on Sideswipe’s aft.

     “Yeah… thought you’d say that.” Sideswipe wiggles again before rising up, nearly completely off Grimlock’s spike. Then he slowly sinks back down, both of them moaning at the penetration. When Sideswipe is fully seated once more, he swivels his hips, stirring the spike within him.

     “Scrap. Oh, scrap,” Grimlock whimpers.

     “Yup,” Sideswipe agrees and does it all over again. And again. And again, each time moving with more surety until Sideswipe is steadily bouncing on Grimlock’s spike. The other mech’s hands stay busy, sliding up Grimlock’s shoulders and down his chest, dipping into transformation seams and tickling their edges.

     All Grimlock can do is hold on for the ride. Sideswipe is smaller than him and while agile and quick, he’s not built as tough as a Dinobot. Grimlock worries that he’ll grip him too hard, or thrust up too roughly. So he mostly stays still, but does allow his hands to wander.  

     “Oh, frag,” Sideswipe moans, hips still moving even as his head falls back. “That is so… good…”

     “Mmm,” Grimlock hums in agreement, leaning forward and laving the side of Sideswipe’s bared throat. Sideswipe tilts his head to the side and pulls him closer in invitation. Grimlock happily obliges, sliding his hands up Sideswipe’s back and nibbling the side of his neck.

     That ball of tension at the base of Grimlock’s back strut winds tighter and tighter. He wishes he could last forever, but Sideswipe had revved him up quite a bit with his mouth. His pelvis starts involuntarily rocking with Sideswipe’s movements, meeting each one of Sideswipe’s drops.

     “Oh, yeah… frag yeah,” Sideswipe mutters, arching so that the tip of his spike rubs against Grimlock’s ventrum. Grimlock shifts back a fraction, working his hand between them and captures the throbbing length.  

     Sideswipe shudders, biting his lower lip until it dents. He’s moving more quickly now, chest heaving with his ventilations. Pre-fluid slicks the head of his spike and Grimlock rubs his thumb around it in a circular fashion.

     “You wanna… wanna overload in me? Or maybe… maybe my mouth?” Sideswipe asks, reaching back to rest a hand on Grimlock’s knee for better leverage. His hips move like something out of a pornvid Grimlock saw once and he doesn’t know he ever got so lucky.

     Grimlock reaches up and cups the side of Sideswipe’s face, thumb swiping over that shiny lower lip. Tempting, but… “In you,” Grimlock quickly decides. “Wanna feel you around me.”

     “Can do,” Sideswipe says with a quirk of his lips and Grimlock can resist no longer. He pulls Sideswipe to him, mouth descending onto the other mech’s.

     He’s barely made contact when Sideswipe jerks away and shoves at Grimlock’s chest. He immediately draws back to see Sideswipe staring up at him, optics wide and wary.

     “No. Don’t kiss me on the lips,” Sideswipe warns and his voice brokers no argument.

     “Ok,” Grimlock agrees because Sideswipe is warm and trembling in his lap and Grimlock can live without kissing as long as he gets to keep the rest of him. “Can I bite you?”

     Sideswipe blinks at him rapidly before relaxing and beginning to move again. “Go for it.”

     Grimlock purrs in eagerness, leaning back down to nibble on the edge of Sideswipe’s shoulder. The other mech smells so good: heated ozone and the really expensive wax from the nearby car detailer. He tastes even better, Grimlock decides, glossa worming between Sideswipe’s transformation seams and licking at tension wires running from his neck to arm.

     Sideswipe makes a faint sound of approval and his hips bounce faster. “Good… that’s good, Grim.”

     Rumbling at the praise, Grimlock continues to lick and nibble, nipping at the edge of Sideswipe’s jaw. The smaller mech’s engine revs and he clutches Grimlock’s shoulders, valve beginning to tighten.

     “Oh, frag… I’m close… you?”

     Grimlock grips Sideswipe’s aft tighter, optics shutting as the snug channel around his spike ripples from base to tip. “Uh huh.”

     He desperately nuzzles Sideswipe’s neck, wishing he could move. Every instinct within him is screaming for him to topple them forwards so that Grimlock could really drive into Sideswipe. But he holds back.

     He will not hurt Sideswipe. He will not.

     Sideswipe’s hand rises up and he lays it on the back of Grimlock’s helm, pressing him closer to Sideswipe’s shoulder.

     “Come on…” Sideswipe murmurs. “Thought you wanted to bite me.”

     Grimlock’s denta scrape against one another excitedly. He’s been given permission twice now and he can’t resist. He opens his jaws and fits them over Sideswipe’s neck, nudging the other mech’s head back. And he bites, sharpened denta piercing Sideswipe’s plating. Droplets of energon flit across Grimlock’s glossa and he moans excitedly as Sideswipe jerks in his grip.

     “Frag! Yes, yes!” Sideswipe shouts and slams his pelvis down, circling his hips. A warmth blooms between their bellies and Sideswipe’s valve spirals tight, rhythmically milking Grimlock’s spike.

     His vision fritzes at the sensation and he bites harder, his own spike twitching and then releasing his spill deep inside Sideswipe. Dimly he hears someone whining and after a few moments he realizes that it’s him. He doesn’t care. Sideswipe fits inside his arms as if built for them, and Grimlock never wants this moment to end.

     Sadly, it eventually does. The tension leaves his body as his transfluid tank empties and he sags in place, cradling Sideswipe close. The red mech is just as limp, valve channel still clenching spasmodically.

     “Mmmm…” Sideswipe moans, rocking his hips a little. “That… was _awesome_. Hey… let go?”

     The hand on Grimlock’s helm forms a fist and gently thumps the back of his head. Grimlock then realizes that it’s not just a few drops of energon in his mouth, but actually a steady trickle and he carefully loosens his jaws. He draws back and stares at Sideswipe’s neck in horror, the plating coated with a light sheen of energon.

     “Oh… oh scrap, Sides, I didn’t mean to…” he begins to stammer, but Sideswipe’s hand slides around Grimlock’s helm to lay a finger over his mouth.

     “It’s fine. I asked you to and it was perfect,” Sideswipe says. He wears a dreamy sort of smile and doesn’t seem to be bothered in the least by the deep bite.

     Nevertheless, Grimlock had vowed not to hurt Sideswipe and he had done it anyway. He reaches up and mournfully traces the puncture marks. Sideswipe captures Grimlock’s wrist and pulls his hand in front of him so that Sideswipe can nibble at the tip of Grimlock’s index finger.

     “Really. I don’t mind. Although next time, I get to do the biting,” Sideswipe says, optics lighting up playfully as he nips the digit tip.

     “Next time?” A thrill of hope rushes through Grimlock. This wasn’t just a one-time fling? He could have Sideswipe again?

     “Yeah. Unless you don’t want to,” Sideswipe replies, a flicker of unease passing over his face.

     “Oh, no, I want to,” Grimlock rushes to say.

     Sideswipe beams up at him. “Great! Cuz I definitely had fun. So… wanna go again?”

     The red mech’s smile is devious as he rocks his hips. Grimlock’s spike is on its way to depressurization, but it gives an interested twitch anyway.

     “Can I…?”

     Sideswipe cocks his head to the side inquisitively as words fail Grimlock. “What, bud? What do you want? You’ll find I’m open to pretty much anything.”

     Grimlock licks his lips nervously. “Could I… I really want to taste you.”

     “Yeah?” Sideswipe leans back against Grimlock’s encircling arm and Grimlock lets him because Sideswipe is sliding a hand down his own abdomen with a wink and a leer. His fingers bracket his valve, lightly brushing over the base of Grimlock’s spike. A mix of fluids is beginning to seep out around it now that it isn’t so engorged.

      Sideswipe coats two of his fingers in the fluids and holds them up. Grimlock automatically bends his head and parts his lips, but Sideswipe draws his hand to his own  mouth. His optics shutter halfway closed and he moans as he sucks on his digits. Grimlock’s mouth goes dry as Sideswipe makes a point of swallowing. When Sideswipe pulls his fingers free, giving the tips a quick swipe with his glossa, Grimlock whimpers.

      “That?” Sideswipe asks with a challenging quirk of one orbital ridge.

      “Please…” Grimlock breathes. “And…?”

      Sideswipe pauses in the midst of rising up off Grimlock’s lap. “And?”

      Grimlock ducks his head, spark spinning wildly. Sideswipe will think him perverted. He can’t say it.

      Sideswipe rises the rest of the way off Grimlock’s spike and he catches sight of the rivulets of fluid that run down Sideswipe’s legs. Then Grimlock’s sight is blocked when Sideswipe crowds in close between Grimlock’s thighs. He drapes his arms over Grimlock’s shoulders and looks down at him.

      Even though Grimlock is taller, broader, and overall bigger, the position makes him feel safe. It’s just the two of them, close and intimate, and Sideswipe’s expression is expectant, not judging.

      “Go on, tell me,” Sideswipe urges.

      “Can… can I… transform and do that?” Grimlock hesitantly gets out.

      To his surprise, Sideswipe’s optics light up and his intakes hitch in excitement. “Frag yeah, you can,” he says faintly. “We’ll switch out, I’ll sit where you are now so you can reach me better.”

      Sideswipe immediately backs away, tugging on Grimlock’s arm. As Grimlock stands, Sideswipe pushes past him and flings himself onto the rock ledge. He leans back and spreads his thighs, valve lips swollen and glistening.

      “Come on, big boy. I wanna see what that glossa of yours can do.”

 

~ End chapter 

**Notes for the Chapter:**

> Sideswipe is a manipulative little shit. He has good intentions - he and Sunstreaker would literally check each other over after getting injured, which always lead to them interfacing. It was an affirmation of their bond with one another, but Grimlock doesn't know that. He's a little more inexperienced and Sideswipe basically overwhelms him with pleasure. Not that Grimlock hadn't been interested in interfacing with Sideswipe, but still. Potentially dub-con as a just in case.
> 
> Bestiality for Grimlock wanting to eat Sideswipe out while in full dino form; not actually shown.


End file.
